DevTools: always do partial viewport update in console

third_party/WebKit/Source/devtools/front_end/console/ConsoleViewport.js

Index: third_party/WebKit/Source/devtools/front_end/console/ConsoleViewport.js
diff --git a/third_party/WebKit/Source/devtools/front_end/console/ConsoleViewport.js b/third_party/WebKit/Source/devtools/front_end/console/ConsoleViewport.js
index 3388cd73f3779e16cabf143a725430296e9543e6..4dc94938fc8b60d9bdc33211f90d1d219b4a4186 100644
--- a/third_party/WebKit/Source/devtools/front_end/console/ConsoleViewport.js
+++ b/third_party/WebKit/Source/devtools/front_end/console/ConsoleViewport.js
@@ -321,7 +321,6 @@ Console.ConsoleViewport = class {
 
     var visibleFrom = this.element.scrollTop;
     var visibleHeight = this._visibleHeight();
-    var isInvalidating = !this._cumulativeHeights;
 
     for (var i = 0; i < this._renderedItems.length; ++i) {
       // Tolerate 1-pixel error due to double-to-integer rounding errors.
@@ -331,8 +330,6 @@ Console.ConsoleViewport = class {
         delete this._cumulativeHeights;
     }
     this._rebuildCumulativeHeightsIfNeeded();
-    var oldFirstActiveIndex = this._firstActiveIndex;
-    var oldLastActiveIndex = this._lastActiveIndex;
     var activeHeight = visibleHeight * 2;
     // When the viewport is scrolled to the bottom, using the cumulative heights estimate is not
     // precise enough to determine next visible indices. This stickToBottom check avoids extra
@@ -366,10 +363,7 @@ Console.ConsoleViewport = class {
       this._contentElement.style.setProperty('height', '10000000px');
     }
 
-    if (isInvalidating)
-      this._fullViewportUpdate(prepare.bind(this));
-    else
-      this._partialViewportUpdate(oldFirstActiveIndex, oldLastActiveIndex, prepare.bind(this));
+    this._partialViewportUpdate(prepare.bind(this));
     this._contentElement.style.removeProperty('height');
     // Should be the last call in the method as it might force layout.
     if (shouldRestoreSelection)
@@ -381,44 +375,21 @@ Console.ConsoleViewport = class {
   /**
    * @param {function()} prepare
    */
-  _fullViewportUpdate(prepare) {
-    for (var i = 0; i < this._renderedItems.length; ++i)
-      this._renderedItems[i].willHide();
-    prepare();
-    this._renderedItems = [];
-    this._contentElement.removeChildren();
-    for (var i = this._firstActiveIndex; i <= this._lastActiveIndex; ++i) {
-      var viewportElement = this._providerElement(i);
-      this._contentElement.appendChild(viewportElement.element());
-      this._renderedItems.push(viewportElement);
-    }
-    for (var i = 0; i < this._renderedItems.length; ++i)
-      this._renderedItems[i].wasShown();
-  }
-
-  /**
-   * @param {number} oldFirstActiveIndex
-   * @param {number} oldLastActiveIndex
-   * @param {function()} prepare
-   */
-  _partialViewportUpdate(oldFirstActiveIndex, oldLastActiveIndex, prepare) {
-    var willBeHidden = [];
-    for (var i = 0; i < this._renderedItems.length; ++i) {
-      var index = oldFirstActiveIndex + i;
-      if (index < this._firstActiveIndex || this._lastActiveIndex < index)
-        willBeHidden.push(this._renderedItems[i]);
-    }
+  _partialViewportUpdate(prepare) {
+    var orderedItemsToRender = [];
+    for (var i = this._firstActiveIndex; i <= this._lastActiveIndex; ++i)
+      orderedItemsToRender.push(this._providerElement(i));
+    var willBeHidden = this._renderedItems.filter(item => !orderedItemsToRender.includes(item));

[lushnikov, 2017/02/14 21:37:51]

this will be faster with a Set()

[luoe, 2017/02/14 22:23:46]

Done.

     for (var i = 0; i < willBeHidden.length; ++i)
       willBeHidden[i].willHide();
     prepare();
     for (var i = 0; i < willBeHidden.length; ++i)
       willBeHidden[i].element().remove();
 
-    this._renderedItems = [];
-    var anchor = this._contentElement.firstChild;
     var wasShown = [];
-    for (var i = this._firstActiveIndex; i <= this._lastActiveIndex; ++i) {
-      var viewportElement = this._providerElement(i);
+    var anchor = this._contentElement.firstChild;
+    for (var i = 0; i < orderedItemsToRender.length; ++i) {
+      var viewportElement = orderedItemsToRender[i];
       var element = viewportElement.element();
       if (element !== anchor) {

[einbinder, 2017/02/14 19:08:46]

It looks like wasShown can be called on things that weren't hidden in the first
place. Is that intentional?

[lushnikov, 2017/02/14 21:37:51]

That's a good call. We probably want calls willHide() and wasShown() to be
symmetrical

[luoe, 2017/02/14 22:23:46]

Good point, there's no need for wasShown if the element was already inserted!

[luoe, 2017/02/14 22:23:46]

Done.

         this._contentElement.insertBefore(element, anchor);
@@ -426,10 +397,10 @@ Console.ConsoleViewport = class {
       } else {
         anchor = anchor.nextSibling;
       }
-      this._renderedItems.push(viewportElement);
     }
     for (var i = 0; i < wasShown.length; ++i)
       wasShown[i].wasShown();
+    this._renderedItems = orderedItemsToRender;
   }
 
   /**